In the Legos Example, the most accurate sample technique was: Guessing the mean Drawing a “convenient” sample Drawing random samples

What kind of problems can bias a survey? 1.Undercoverage 2. Judgment sample 3. Convenience Sample 4. Voluntary response 5. Non-response 6. Response bias

Why do medical studies use double blind studies To remove bias in selecting patients who receive treatment To remove bias in handling patients Both (a) and (b) Other biases

Probability sample vs Non-probability samples Some types of sampling SRS Simple Random Sample Stratified sample Clustered sample Systematic sample Probability sample vs Non-probability samples

If I go to the campus center cafeteria and poll every 4th person I run into, I’ll end up with a random sample of all the students at the university stratified sample of the student population A biased sample of students at the university

It is always better to take a census to draw a sample

Precision Sample size: determines how well the sample represents the population. Accuracy of data is inversely proportional to the square root of the sample size

A poll taken at our favorite web site: www. statsisfun A poll taken at our favorite web site: www.statsisfun.org gathered 12,357 responses. The majority said they enjoy doing statistics homework. With a sample size that large, we can be pretty sure that most statistics students feel this way too. Yes no

We need to survey a random sample of the 300 passengers on a flight from San Francisco to Tokyo. Match each method below with its proper method name

1. Pick every 10th passenger 2 1. Pick every 10th passenger 2. From the boarding list randomly choose 5 people flying 1st class and 25 other passengers 3. Randomly generate 30 seat numbers 4. Randomly select a seat position (a,b,c,e,f,g,h,i) and survey all passengers sitting in those seats Random Cluster Systematic Stratified